"Prism cannot start because the display resolution is too low. " or "Prism cannot start because the current DPI setting is too high".

Prism 7 requires a minimum display height of 540 pixels.Prism Windows 6  and Prism 5 (starting with 5.03) run in a screen as small as 800 x 576. Earlier releases of Prism 5 required a larger screen, so update to the latest. 

The message can occur for several reasons:

• Your screen really is too small.
• Prism is mixed up about landscape vs. portrait, so thinks there is not enough space.
• You are running Windows on Parallels or Fusion (on a Mac) and have made the Windows window too small.
• You are  using a screen that is large enough but have set the text size too large. This page explains how to reduce the text size in Windows 8. 

Alternative workarounds for Prism 6 and 7:

• Right click on the Prism application icon, choose properties, go to the  Compatibility tab and check the option: "Disable display scaling on high DPI setting".
•  Go to the control Panel… Display... Screen resolution... Make text and other items larger or smaller, and set DPI settings to a lower value. You may need to try a few values to find one that works for you. Note that this setting is confusing. If you choose a high dpi, everything is shown larger on the display, so large dialogs (and Prism has some) won't fit. So while it seems as though increasing this number increases the resolution, in fact it decreases the resolution. Very high values make everything so large that Prism won't fit on the display. 
• Windows Vista/7/8. Go to the control Panel… Display... Screen resolution... Make text and other items larger or smaller. Check combo box “Use Windows XP style DPI scaling” on.

Two workarounds if your desired settings doesn't quite leave enough room for the large Prism dialogs:

• If the Windows task bar is at the bottom of the screen, it will take up some space Prism could be using. You can change its setting so it autohides. Better, consider moving the task bar to the right or left side of your display rather than across the bottom.
• If some dialogs appear too large on screen (given your settings), you may still be able to get your work done. Only the bottom part of large Prism's dialogs will be cut off, which means you can't see the Help, Cancel, or OK buttons. Instead use the keyboard: Click the F1 key for help, the Esc key for Cancel, and the Enter key  for OK.